The cypress bark beetle, Phloeosinus aubei, is of increasing concern in the European market of scale‐leafed conifers. Neither the reproductive behaviour nor the chemical ecology have been studied in ...detail so far, and no specific attractant traps are available to monitor the flight of adults. We established that stridulation by males is crucial for acceptance by calling females. To unravel the chemical communication, hindgut extracts from unmated females were analysed by GC‐EAD, using male antennae. Gut extracts and Thuja occidentalis leaf extracts were analysed by GC/MS. Two antennally active compounds from gut extracts were identified as (−)‐myrtenol and (−)‐α‐pinene by enantioselective GC/MS. (−)‐Myrtenol was shown to be female‐specific, while (−)‐α‐pinene was found as a 2:1 mixture with the (+)‐enantiomer also among the volatiles of the host tree, T. occidentalis. To prove that the production of the above compounds in the beetles is related to reproduction, we treated females with JHIII. The gut extracts from these sexually mature females showed elevated levels of (−)‐α‐pinene compared to untreated control groups. Synthetic enantiomers of myrtenol and α‐pinene were tested separately by electroantennography, and all were found to be electrophysiologically active. The attractiveness of different mixtures of these compounds was compared using 4‐arm olfactometer tests: 4:1 mixtures of racemic α‐pinene with either (−)‐ or (+)‐myrtenol were significantly attractive to males and females, respectively. In field tests, multifunnel traps baited with a 5:1 mixture of (−)‐α‐pinene and (−)‐myrtenol caught significantly more males and females than unbaited control traps. We concluded that (−)‐α‐pinene and (−)‐myrtenol are components of a female‐produced aggregation pheromone. EAD activity and behaviour assays indicated that α‐pinene from Thuja is used by the beetles as part of a host plant kairomone. The complex communication system of P. aubei is discussed in a chemoecological context.
Many wood-boring insects use aggregation pheromones during mass colonization of host trees. Bark beetles (Curculionidae: Scolytinae) are a model system, but much less is known about the role of ...semiochemicals during host selection by ambrosia beetles. As an ecological clade within the bark beetles, ambrosia beetles are obligately dependent on fungal mutualists for their sole source of nutrition. Mass colonization of trees growing in horticultural settings by exotic ambrosia beetles can occur, but aggregation cues have remained enigmatic. To elucidate this mechanism, we first characterized the fungal associates of the exotic, mass-aggregating ambrosia beetle
in Southern Germany. Still-air olfactometer bioassays documented the attraction of
to its primary nutritional mutualist
and to a lesser extent another common fungal isolate (
sp.). During two-choice bioassays,
was preferentially attracted to branch sections (i.e., bolts) that were either pre-colonized by conspecifics or pre-inoculated with
. Subsequent analyses identified microbial volatile organic compounds (MVOCs) that could potentially function as aggregation pheromones for
. To our knowledge, this is the first evidence for fungal volatiles as attractive cues during host selection by
. Adaptive benefits of responding to fungal cues associated with an infestation of conspecifics could be a function of locating a suitable substrate for cultivating fungal symbionts and/or increasing the likelihood of mating opportunities with the flightless males. However, this requires solutions for evolutionary conflict arising due to potential mixing of vertically transmitted and horizontally acquired symbiont strains, which are discussed.
The migratory locust, Locusta migratoria (L. migratoria), is one of the most damaging agricultural pests worldwide. Currently, the monitoring of L. migratoria largely depends on the labor-intensive ...field survey and remote sensing with insufficient spatial precision. A sensitive and real-time monitoring technology is desired for early detection and efficient management of the infestation. Here we characterized peptide sequences of the L. migratoria odorant receptor that can recognize the aggregation pheromone 4-vinylanisole (4 VA) by molecular docking. Next, we designed odorant receptor-derived peptides (ORPs) and fabricated an ORP-biosensor capable of real-time monitoring of gaseous 4 VA with high sensitivity (∼1 ppb) and selectivity. Furthermore, we demonstrated that the ORP-sensor could detect a single live L. migratoria and observed that the feeding behavior of L. migratoria accelerated the release of 4 VA, which provided a new evidence for the viewpoint that locust aggregation behavior was regulated by food resources. The findings suggest the potential applications of ORP-sensors in entomology research, infestation control and other areas where the detection of a gaseous substance is needed.
•The ORPs for recognizing locust aggregation pheromone 4 VA were designed and synthesized.•The fabricated ORP-sensor enabled detection of gaseous 4 VA at concentration of 1 ppb with excellent selectivity.•The fabricated ORP-sensor could detect 4 VA released by a single live L. migratoria in real time.•It was discovered that the feeding behavior of L. migratoria accelerated the release of 4 VA.•The ORP-sensor had potential applications for entomology and infestation control.
The aggregation pheromone 4,8-dimethyldecanal (4,8 DMD) used alone or with kairomone-baited traps generally is used for monitoringTribolium castaneum (Herbst) but low efficiency is reported. ...Furthermore, insect orientation to pheromones and kairomones following low or high temperature exposure is not yet understood. This research evaluated the orientation of T. castaneum adults to 4,8 DMD and common kairomones following exposure to ambient, low or high temperatures. Fifty adults were introduced to the middle of rectangular glass chamber, and movement to the treatment or control was determined after 1 h. In experiment 1, insects reared at 30°C were used. Experiments 2 and 3 used insects exposed to 10°C for 4 days (cold temperature) and 42°C for 12 h (brief high temperature), respectively at 2–8 h following cold or heat exposure. The highest trapping occurred when 4,8DMD was combined with neem oil whereas the lowest was in coconut oil alone. Neem oil alone demonstrated repellent action. Prior exposure to cold or heat initially reduced taxis of T. castaneum adults to traps. The attraction for adults exposed to cold and heat was restored after 6–8 h when traps contained pheromone + neem or coconut oil. This study marks the first to experimentally test how exposure to high or low temperatures, two key IPM tactics in the post-harvest supply chain, affects the behavioral response of an important stored-product species to pheromone- and kairomones-baited traps.
•4,8-DMD with kairomones, coconut oil or neem oil enhanced T. castaneum trapping.•Pre-exposure to high or low temperature affects orientation of T. castaneum adults.•High/low temperature increased T. castaneum adults trapped after initial decrease.
Palm trees are of immense economic, sociocultural, touristic, and patrimonial significance all over the world, and date palm‐related knowledge, traditions, and practices are now included in UNESCOs ...list of the Intangible Cultural Heritage of Humanity. Of all the pests that infest these trees, the red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), is its primary enemy. The RPW is a category‐1 quarantine insect pest that causes enormous economic losses in palm tree cultivation worldwide. The RPW synchronizes mass gathering on the palm tree for feeding and mating, regulated by a male‐produced pheromone composed of two methyl‐branched compounds, (4RS, 5RS)‐4‐methylnonan‐5‐ol (ferrugineol) and 4(RS)‐methylnonan‐5‐one (ferrugineone). Despite the importance of odorant detection in long‐range orientation towards palm trees, palm colonization, and mating, the pheromone receptor has not been identified in this species. In this study, we report the identification and characterization of the first RPW pheromone receptor, RferOR1. Using gene silencing and functional expression in Drosophila olfactory receptor neurons, we demonstrate that RferOR1 is tuned to ferrugineol and ferrugineone and binds five other structurally related molecules. We reveal the lifetime expression of RferOR1, which correlates with adult mating success irrespective of age, a factor that could explain the wide distribution and spread of this pest. As palm weevils are challenging to control based on conventional methods, elucidation of the mechanisms of pheromone detection opens new routes for mating disruption and the early detection of this pest via the development of pheromone receptor‐based biosensors.
Chemical signals from conspecifics are essential in insect group formation and maintenance. Migratory locusts use the aggregation pheromone 4-vinylanisole (4VA), specifically released by gregarious ...locusts, to attract and recruit conspecific individuals, leading to the formation of large-scale swarms. However, how 4VA contributes to the transition from solitary phase to gregarious phase remains unclear. We investigated the occurrence of locust behavioral phase changes in the presence and absence of 4VA perception. The findings indicated that solitary locusts require crowding for 48 and 72 h to adopt partial and analogous gregarious behavior. However, exposure to increased concentrations of 4VA enabled solitary locusts to display behavioral changes within 24 h of crowding. Crowded solitary locusts with RNAi knockdown of
Or35
, the specific olfactory receptor for 4VA, failed to exhibit gregarious behaviors. Conversely, the knockdown of
Or35
in gregarious locusts resulted in the appearance of solitary behavior. Additionally, a multi-individual behavioral assay system was developed to evaluate the interactions among locust individuals, and four behavioral parameters representing the inclination and conduct of social interactions were positively correlated with the process of crowding. Our data indicated that exposure to 4VA accelerated the behavioral transition from solitary phase to gregarious phase by enhancing the propensity toward proximity and body contact among conspecific individuals. These results highlight the crucial roles of 4VA in the behavioral phase transition of locusts. Furthermore, this study offers valuable insights into the mechanisms of behavioral plasticity that promote the formation of locust swarms and suggests the potential for 4VA application in locust control.
Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is one of the major pests of soybean (Glycine max L. Merr.) in Korea and Japan. The occurrence of two important egg parasitoids of R. pedestris, ...Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae), before and after soybean cultivation is poorly known. To record the seasonal occurrences of R. pedestris and parasitism during 2008–2010, aggregation pheromone traps baited with R. pedestris eggs were placed in a field in Andong, Korea where a series of crops, including barley (Hordeum vulgare L.), sesame (Sesamum indicum L.), and soybean, were cultivated during this study. R. pedestris was first recorded in the second week of April on barley and was most abundant in August on soybean. G. japonicum first appeared in May and was the dominant parasitoid until the first week of August on barley, sesame, and early soybean. From late August to September or October when soybean was cultivated, O. nezarae became the dominant parasitoid. The differential pattern of seasonal occurrence between the two parasitoids is discussed.
► Aggregation pheromone trap baited with bean bug eggs was used to monitor parasitism. ► Bean bug was first found in April on barley and most abundant in August on soybean. ► Gryon japonicum first appeared in May and was the dominant parasitoid until August. ► From late August, Ooencyrtus nezarae became the dominant parasitoid on soybean. ► Differential pattern of seasonal occurrence between the two species is new finding.
The recent outbreak of the mountain pine beetle (Dendroctonus ponderosae; MPB) has affected over 20 M hectares of pine forests in western North America. During the colonization of host trees, female ...MPB release the aggregation pheromone (-)-trans-verbenol. (-)-trans-Verbenol is thought to be produced from the pine defense compound (-)-α-pinene by cytochrome P450 (P450) dependent hydroxylation. MPB may also use P450s for the detoxification of other monoterpenes of the pine defense system. Here we describe the functional characterization of MPB CYP6DE1. CYP6DE1, but not the closely related CYP6DE2, used the bicyclic monoterpenes (-)-α-pinene, (+)-α-pinene, (-)-β-pinene, (+)-β-pinene and (+)-3-carene as substrates. CYP6DE1 was not active with other monoterpenes or diterpene resin acids that were tested as substrates. trans-Verbenol is the major product of CYP6DE1 activity with (-)-α-pinene or (+)-α-pinene as substrates. When tested with blends of different ratios of (-)-α-pinene and (+)-α-pinene, CYP6DE1 produced trans-verbenol with an enantiomeric profile that was similar to that produced by female MPB exposed to the α-pinene enantiomers.
Display omitted
•Synthesis of cerambycid pheromone: 3-hydroxy-2-hexanone and 2,3-hexanediol.•α-Hydroxylation of several alkylketones using (diacetoxyiodo)benzene.•Chiral synthesis of ...(R)-3-hydroxy-2-hexanone using l-proline as a catalyst.
The synthesis of 3-hydroxy-2-hexanone and 2,3-hexanediol, two components of the aggregation pheromone of several cerambycid species, is disclosed in here. Starting from 2-hexanone, through an α-hydroxylation using (diacetoxyiodo)benzene, 3-hydroxy-2-hexanone is obtained in good yield. Further reduction of this compound, gives 2,3-hexanediol in excellent yield. A study of the α-hydroxylation reaction of several alkylketones using an hypervalent iodine reagent is also disclosed in here. The synthesis of optically active compounds (R)- and (S)-3-hydroxy-2-hexanone was achieved starting from 2-hexanone with nitrosobenzene and l- and d-proline respectively, in several reaction media.
PDF
